Metabolites identification of harmane in vitro/in vivo in rats by ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

• Systematically investigate the metabolites of harmane in vivo and in vitro.
• Metabolites of harmane were identified by UPLC/ESI-QTOF-MS.
• CLogP combined with specific pH of flow phase was used to distinguish metabolites.
• Hydroxylation, N-oxidation, O-glucuronide, O-sulphate, and glutathione conjugation.
• Harmine and harmol were not found as metabolites of harmane in rat.

Harmane, a β-carboline alkaloid with a wide spectrum of pharmacological activities, is naturally present in the human diet, in numerous foodstuffs and in hallucinogenic plants such as Peganum harmala, Banisteriopsis caapi and Tribulus terrestris. However, the precise metabolic fate of harmane remains unknown. In order to know whether harmane is extensively metabolized, a rapid and sensitive method using ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC/ESI-QTOF-MS) was used to analyze the metabolic profile of harmane in vitro and in vivo in rats. A total of 21 metabolites were identified from the rat liver microsomes and rat liver S9 (9), rat urine (11), feces (16), bile (16), and plasma (10) after a single oral administration of harmane using MetaboLynx™ and MassFragment ™ software tools. It indicated that the biliary and faecal clearance were the major excretion routes for harmane as well as its metabolites. The specific CLogP values combined with different acidic and alkaline mobile phase were helpful and useful for distinguishing N-oxidation and monohydroxylation metabolites. The metabolic transformation pathways of harmane included monohydroxylation, dihydroxylation, N-oxidation, O-glucuronide conjugation, O-sulphate conjugation, and glutathione conjugation. In conclusion, this study showed an insight into the metabolism of harmane.

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